Showing papers on "Magnetic circuit published in 1975"

The magnetic circuit of an axial field D.C. electrical machine

Abstract: A permanent magnet d.c. machine is described, with an axial field and a disc-shaped armature. The potential distribution is calculated in three-dimensions for high-coercivity magnets, for which a uniform intrinsic magnetisation can be assumed. This shows the importance of not assuming a constant potential over the pole surface, and of not reducing the system to two-dimensions. The field in the air-gap is found, and a comparison of magnet shapes shows that commonly used circular poles produce poor values of useful field. A compacted mixture of iron powder and epoxy resin has been found to be a good substitute for laminations in the magnetic circuit. It is shown that this material carries about the same flux in the machine as does mild steel. However, it offers a significant reduction in the eddy-current and hysteresis losses, compared with laminated nickel iron.

Electrodynamic type electroacoustic transducer

Abstract: An electrodynamic type electroacoustic transducer wherein a diaphragm of a nonmagnetic and insulative material having thereon a series of conductors is disposed between a pair of magnetic circuits opposing one another through a slight clearance so that the conductors will lie in magnetic flux flowing between opposite polarity ends of at least a pair of permanent magnets in each magnetic circuit and will move in directions transverse the flux when the diaphragm is vibrated, in which the diaphragm is resiliently held in said clearance by means of an elastic support means inserted at least between the diaphragm and the respective opposing pole ends of the magnets in both circuits so as to be prevented from contacting the pole ends when vibrated. Preferably said means on sound-passing side of the magnetic circuit is a disk-shaped pad of glass fiber or the like and the one on non-sound-passing side circuit is glass fiber or the like filled in spaces defined by the diaphragm and the magnets and soft iron plate coupling them in the circuit so as to absorb sounds.

Dynamoelectric machinery utilizing superconductive windings

Abstract: Iron or other ferromagnetic material is utilized in the magnetic circuit of dynamoelectric machines having superconductive field or excitation windings. In DC machines, a stationary salient pole field structure with a superconductive main field winding is utilized. An armature winding is wound about a smooth rotor. In AC machines, a ferromagnetic structure that encloses and rotates with a superconductive excitation winding is utilized. The ferromagnetic structure may include either salient poles interconnected by ferromagnetic shunts or a slotted or toothed rotor.

Saturable reactor current limiter

Abstract: A current limiter to protect circuit elements from excessive current caused by transient load impedance or power supply surges. A multiple branch element magnetic circuit includes at least one saturable branch element inductively coupled by a coil connected in series with the load of an external electric circuit. The magnetic circuit further includes lower permeance bias branch element which biases the saturable branch element in a low permeance, saturated state when current through the coil is below a predetermined threshold value, and which biases at least one saturable branch element in its high permeance, non-saturated state when current through the coil is in a predetermined range above and extending from the threshold value. A relatively high permeance shunt branch element provides a shunt path for magnetic flux. The coil provides a relatively high inductive impedance in series with the external electrical circuit when at least one saturable element is in its non-saturated state and provides a relatively low impedance otherwise.

Narrow track MR head with side shields

Abstract: A magnetic head consists of a magnetic flux converging core having a magnetic gap and a magnetoresistive effect element which forms a magnetic circuit and which is arranged in the same plane as the magnetic gap. The direction of thickness of the magnetic circuit is aligned with the direction of width of a track of a record medium, and shielding plates of ferromagnetic material are arranged on both sides of the plane.

High density flux magnetic circuit

Abstract: Magnetic means and circuits for efficiently conducting and directing flux to a flux emergent surface, such as the pole of a motor pole piece, in which flux produced by one or more permanent magnetic sources matched in reluctance to a working air gap is directed through an essentially continuously curved convex surface of a volume of magnetically permeable material significantly greater in area than the area of the working air gap, with the flux from the magnetic source(s) is generally everywhere normal to that surface.

Magnetic induction stringed instrument pickup

Abstract: A magnetic induction type electrical pickup for a stringed musical instrument has two coils each having an opening receiving one or more permanent magnet elements. The magnet elements establish a magnetic circuit through the two coils the reluctance of which is varied by the vibration of a string to induce signal voltages in the coils. The arrangement and polarities of the permanent magnet elements, and the arrangement, winding direction and interconnection of the two coils is such as to minimize the effect of stray magnetic fields, having any random direction, on the output of the pickup. That is, the pickup is one which is highly effective in suppressing noise arising from ambient magnetic fields generated by nearby electrical devices. Also, microphonics or squeals are inhibited by construction features which repress resonant vibration of internal parts of the pickup.

Finite-element solutions for devices with permanent-magnets

Abstract: The magnetic field of a complicated magnetic circuit consisting of both electromagnets and permanent magnets situated in air can be derived from the solution of a boundary value problem. Such a problem can be formulated so as to find a potential function giving a stationary value to an appropriate functional. A numerical solution can then be found by applying the finite-element method. Expressions of the functional for materials with different magnetic properties and the derivation of the numerical solution of the boundary value problem by the finite-element method are given with special emphasis on systems with permanent magnets. In one of the two examples illustrating the application of the method, design considerations of the magnetic device are related to the solution.

Alternating current solenoids

Abstract: A linear acting solenoid directed to energy conservation. The disclosure combines plural elements usable singly or in combination to enable in aggregate a low cost assembly, yielding values of pull-force per watt of input exceeding ten ounces. Size, cost, and temperature rise are reduced, and shading rings are avoided. Novel elements include a composite phase-splitting core, and a unitary magnetic shell forming an efficient divided-path magnetic circuit, the flux therethrough being confluent through armature and core. In valve or other fluid-barrier uses, a thin ferrous armature housing enables pull values exceeding three ounces per watt of input.

Multi-tracks magnetic head with single turn winding structure

Abstract: A multi-tracks magnetic head has a first conductor utilized as the bias winding, and a second conductor as the winding for the signal to be recorded. Only the first conductors of the respective unit magnetic heads are connected in series. By making use of the multi-track magnetic head constructed in this way, electrical power consumption by the amplifiers supplying the recording currents to drive all the composing unit magnetic heads is minimized, and the magnetic cross-talk between the unit magnetic heads is reduced.

Device for the magnetic orientation of magnetic recording media

Abstract: A device for manufacturing magnetic recording media in which the magnetic particles in the recording layer are oriented in a preferred direction, the fluid coating applied to the base being subjected to the action of a magnetic field produced in the air gaps between the spaced apart poles of two magnetic circuits, one on each side of the coated face, arranged symmetrically with respect to the plane of the coated base, the edges of the poles adjacent to the coated base terminating in screening elements shaped in such a way that the distance between the surfaces of the screening elements facing the coated base and the coated base itself increases as the screening elements extend away from the edges of the poles A high degree of magnetic anisotropy in the recording layer can also be obtained when the magnetic circuits are at a relatively large distance from the still fluid magnetic coating

Sputter-ion pump having improved cooling and improved magnetic circuitry

Abstract: In a magnetically confined sputter-ion vacuum pump a multi-apertured anode electrode is interposed between a pair of reactive cathode electrode plates. An evacuable envelope encloses the anode and cathode electrodes and a magnetic circuit surrounds the vacuum envelope for producing a glow discharge confining magnetic field extending axially of the apertures in the anode. The reactive cathode plates include peripheral sealing flanges for compressing a sealing gasket into sealing engagement with a pair of sealing surfaces at opposite ends of a tubular main body portion of the envelope. A clamping ring structure, having a bolt circle formed therein, serves to clamp the two reactive cathode plates to the main body and also serves as an integral part of the magnetic circuit. Water coolant channels are brazed to the outer surfaces of the cathode plates for cooling same in use. The magnetic circuit includes a pair of ferrite magnets disposed outside the envelope on opposite sides of the cathodes and enclosed by a magnetic yoke to minimize the size and weight of the magnet and to reduce unwanted stray magnetic fields.

Circuit interrupter having an electromagnetic repulsion device

Abstract: Circuit interrupter having a magnetic circuit energized by the current flowing through the interrupter and an induction plate that is movable with the movable contact of the interrupter. The abrupt rising of a fault current induces secondary currents in the induction plate which is located in the air gap of the magnetic circuit as long as the interrupter is in the closed-circuit position. The secondary currents tend to expel the induction plate from the air gap thereby moving the movable contact vigorously away from the magnetic circuit.

Flux paths and flux transfer mechanism in the T joints of three phase transformer cores

Abstract: A better understanding of flux behavior within specific regions of a transformer core can lead to improved core design and magnetic efficiency. Flux paths and the flux transfer mechanisms have been determined for two practical T joints of different designs employed in two similar three-phase three limbed transformer cores. Each core was energized at three different core flux densities. The instantaneous flux density patterns both parallel to and perpendicular to the rolling plane of the laminations are presented in graphical and vectorial forms for both types of T joints. By "freezing" the continually changing flux pattern within a T joint, it was possible to trace individual flux paths through the joint and to determine the basic flux transfer mechanism between adjacent laminations. Flux behavior within the joints shows that while its path is dependent on both T joint design and core flux density, the basic flux transfer mechanism remains unchanged in both T joints and at all core flux densities.

Axial and annular magneto-elastic dynamometers

Abstract: An apparatus and method for measuring stresses or forces by measurement of variations of the magnetic properties of ferromagnetic substances under stress conditions. This is carried out by providing a ring of ferromagnetic material between two parallel faces on or between which the stresses are exerted, the ring defining a magnetic circuit, providing an electric coil within and around the ring, passing a current through the coil and measuring changes in the properties of the current to measure variations in the magnetic properties of the ring.

Devices for magnetic control with permanent magnets

Abstract: A magnetic device comprising two permanent magnets, armature members forming with said magnets a closed magnetic circuit and an external air gap, and means for reversing the direction of magnetization of one of the magnets, whereby the flux is prevented to close along the magnetic circuit and caused to close through the air gap, or caused to close along the magnetic circuit, the flux in the air gap then being suppressed. The said means consist of two distinct coils wound about the magnets. One of the coils is energized for establishing the flux in the air gap, while the other coil is energized for suppressing the flux in the air gap.

Electro-magnetic devices

Abstract: An electro-magnet includes a pole-piece having a portion of reduced cross-section. The shape of the reduced portion provides a restriction in the magnetic circuit such that the distance moved, against a biasing force, by an armature of the electro-magnet is proportional to the current in the electro-magnet winding. The pole piece comprises aligned parts of nickel-iron alloy joined by a soft iron part whose cross-section is less than that of the nickel-iron alloy parts.

A rapid method of computation of the magnetic field of permanent magnets

Abstract: A rapid method for the computation of the magnetic field of permanent magnets in the presence of saturable iron cores is described and experience in using it discussed. This method makes use of finite elements and allows for non-uniform magnetisation in the magnet. The factors affecting convergence are examined.

Magnetic pulse type ignition distributor

Abstract: Magnetic pulse type ignition distributor in which the magnetic pulses are oduced by a pole-carrying timer core rotating in the magnetic gap between two stationary poles of a magnetic circuit. The timer core is enclosed in a sealed casing made principally of a non-magnetic metal. The stationary poles enter this casing through openings partially defined by a non-conductive material to avoid heating due to eddy currents. Means are provided for minimizing the friction produced by rotation of the timer core, and for facilitating the mounting of the casing and the remainder of the distributor in a position in which the timing is sufficiently well adjusted to permit operation of the motor.

Linear motor for indicating and writing meters - has stator core embraced by induction winding, and external iron return core

Abstract: Linear motor, partic. for indicating and writing measureing-instruments, comprises a stator core, an induction winding around the stator core, and an external, iron return circuit (core) between which and the winding are arranged permanently magnetised magnets perpendicular to the winding axis. The induction winding is split up into several switch-on switch-off discrete windings on the magnetic circuit open at the axial ends. The permanent manets are arranged, such that one or more stand axially opposite, and at the same height as, the series of windings, and the permanent magnets can be moved along the coils immovably arranged on the stator core. Only those discrete windings having the permanent magnets near to them have current passing through them in the working direction. The permanent magnets are specif. made of anisotropic material.

Electrical pulse generator for remote reading meter

Abstract: Electrical pulse generator to operate a remote water meter indicator in which the pulse generator is driven by the drive of the meter to cause a magnetic circuit to be opened and closed in accordance with the rotation of the meter drive. The magnetic circuit is opened and closed in a manner whereby a linear force element, i.e., a spring, is acting against a magnetic gap so that the spring is sufficient to overcome the magnetic force and open the gap to cause a large change in the reluctance of the magnetic circuit, generating a pulse in a coil which can be then used to drive a remote reading meter.

Magnetic head with thin sheet exhibiting magnetoresistive property

Abstract: A thin ferromagnetic sheet or layer exhibiting magnetoresistance property is connected in the magnetic circuit of a magnetic head including a head or air gap, and a pair of current terminals are attached to the thin ferromagnetic sheet and spaced apart by a predetermined distance from each other so as to flow the current of a predetermined magnitude through the thin ferromagnetic sheet, whereby the variation in magnetic field produced by a magnetic recording medium passing over the head or air gap may be detected in terms of the voltage variation between the current terminals.

Magnetic circuit and method of making

Abstract: A low cost magnetic circuit and method of making the same are disclosed. The magnetic circuit comprises an integral magnetic core having at least four legs in a closed magnetic path, at least one leg thereof with a circular cross section and a bobbin rotatably disposed about the circular portion for containing a coil winding. The coil is formed by rotating the bobbin while holding the core stationary.

Application of integral transforms to the analysis of the magnetic field of a spherical coil

Abstract: The paper discusses the application of the integral transforms method to the analysis of the magnetic field produced by a system of conductors with finite thickness. An example is given for the determination of the magnetic field due to a spherical coil using the Mellin tramsform of the current density distribution function. Obtained formulas for the magnetic field distribution are very useful for numerical computation. In many cases it is necessary to determine the magnetic field of the current flowing in a coil of finite dimensions. It concerns the determination of the field inside and outside the conductors.

Performance of linear induction motors with airgap windings

Abstract: Conventional high-speed linear induction motors designed to operate from a 50 Hz supply possess large leakage reactances. This is because of the large end-winding-overhang/core-width ratio. The resulting poor power-factor performance of these machines may be improved by incorporating the primary end windings into the main magnetic circuit of the machine. Difficulties in construction and low airgap flux density point to the use of airgap windings. A mathematical model is developed, and verified against practical test results, to give the complete electrical and mechanical performance of axial-flux linear machines with 2-dimensional conductor distribution and airgap windings. The treatment makes no assumptions about input current balance. Any number of serially connected coil groups, energised from independent voltage sources, are considered. The model is also suitable for predicting the performance of conventional linear machines and in this case gives improved estimates over previous single-dimensional analyses. The model is used to predict the performance of two equivalent high-speed designs. These results show an improved power factor over a conventional design for an airgap-wound machine with a minimum of coil overhang.

Magnetic circuit apparatus for an electronic ignition system of a combustion engine

Abstract: Magnetic circuit apparatus for use in an electronic ignition system of a combustion engine having one or more spark ignition devices comprises a magnetically permeable frame on which is supported a field magnet and a Hall Effect pulse generator in spaced apart relation such that the field magnet and frame provide a magnetic flux path to which the pulse generator periodically is exposed to produce successive pulses in timed relation to the speed of operation of the engine. A bias magnet confronts the pulse generator at that side of the latter which is opposite to the field magnet and has a polarity opposite that of the field magnet. The flux density of the bias magnet is substantially less than that of the field magnet.

Liquid-level sensor utilizing ferromagnetic fluid

Abstract: The invention is directed to a liquid-level sensor utilizing a ferromagnetic fluid. The magnetic characteristics of the fluid are utilized in a magnetic circuit which generates the output signal and are also useful in the mechanical operation of the sensor. The magnetic characteristics of the ferromagnetic fluid, therefore, serve a twofold purpose in the inventive sensor.

Compact mechanically-powered electric generator for a camera or other apparatus

Abstract: An electrical component, such as a photoflash lamp that is associated with a photographic camera, is energized by an electric current produced by a compact mechanically-driven electric generator that is located within the camera and coupled to the shutter-actuating mechanism. The generator employs a spring-driven keeper that changes the reluctance of a magnetic circuit and causes an associated wire coil to produce a voltage pulse that is synchronized relative to the opening of the camera aperture. The generator is compact enough to fit inside "Instamatic" type cameras and provides a simple, reliable and inexpensive substitute for the batteries now employed in such cameras. The small size and reliability of the generator adapt it for use in other types of devices and systems that require a passive easily-triggered electrical power source.

Supply circuit for electromagnets

Abstract: An improved supply circuit for electromagnets. The supply circuit comprises a bridge rectifier, an attracting winding positioned in the diagonal of the bridge rectifier, a holding winding placed on the magnetic circuit of the electromagnet, and an isolating contact which isolates the bridge at the end of the pulling-in course of the movable member of the magnetic circuit. The holding winding being connected in parallel across the system formed by the isolating contact and the bridge rectifier.

Analysis of flux in electromagnets having rectangular cross-section

Abstract: In electromagnets having rectangular cross-section, the magnetic flux in the airgap is a function of the relations between the geometric dimensions of the exciting coil. Maximum magnetic flux from a given volume can be obtained when the optimum values of the geometric parameters are chosen. The results of the investigation are presented both analytically and graphically in non-dimensional forms for a wide range of electromagnets used in practice.